Mystery aficionados will get a workout while trying to catch all the references to mystery authors and their protagonists in Hart's 11th entry (after Yankee Doodle Dead) in her Agatha Award-winning Death on Demand series. Annie Darling, who owns a mystery bookshop on the barrier island of Broward's Rock, S.C., is appalled when Kathryn Girard, one of the island's Women's Club members, is slain and Annie's friend--and good customer--Henny Brawley, who was injured at the scene, is accused of the crime. Kathryn was supposed to be collecting donations for the annual white elephant sale, but instead she used the Women's Club van to visit the houses of four wealthy families. When Annie and her amateur sleuth husband, Max, discover a stash of thousand-dollar bills in a photo album taken from Kathryn's apartment, they realize that the dead woman had been blackmailing their friends and neighbors. But why? What did the richest of the island's residents have to hide? And who would kill to preserve their secret? As Henny recuperates in the hospital, Annie and Max set out to prove her innocent. Hart's panoply of vivid characters--a tough mystery writer, a dippy mother-in-law, a hard-working single father, an arrogant police chief--makse for entertaining set pieces, but their relationships aren't always fully developed. Moreover, Hart's copious allusions to fellow genre authors and their sleuths becomes distracting. Though no white elephant, this is not prime Hart; still, cozy fans should cotton to it well enough. Author tour. (Sept.)